I. I introduction T he main object of the present paper is a petrological description and a consideration of the genesis of the metamorphic rocks collected by the Cambridge 1926 and 1929 East Greenland Expeditions. 1 The Danish Expedition of 1926-27, under the leadership of Lauge Koch, paid no special attention to the metamorphic rocks,. 2 but a preliminary report of the Danish Expedition of 1929 making good this omission has recently been published. 3 In this report Backlund states that the gneisses of the inner fjord region ‘were formed by mag·matization and syntexis of exceedingly varying sediments by a younger (Caledonian) granite’ (p. 236). He considers, therefore, that most of the metamorphic rocks originated through the assimilation of the Franz Josef Beds by Caledonian granites. It is the aim of this paper to study these ancient gneisses and schists in thin section, in the hope that a better understanding may be obtained both of their metamorphic condition and of their ætiological relations. II. T he W estern M etamobphic C omplex A kyanite-garnet-gneiss was collected from the median moraine of the Nordenskiöld Glacier. Under the microscope, this gneiss is a coarse-grained rock with porphyroblastic crystals of garnet and kyanite. Generally, the garnets exhibit their shape, and are characterized, by an outer rim almost free from inclusions, and an interior region rich in inclusions, especially of quartz, rutile, biotite, tourmaline, and magnetite. The garnets are traversed by two systems of partings, approximately at right angles one to the other. In some individuals the kyanite has been twinned on the